Changelog¶

Versions are year-based with a strict backwards compatibility policy. The third digit is only for regressions.

16.1.0 (2016-08-30)¶

All instances where function arguments were called cl have been changed to the more Pythonic cls. Since it was always the first argument, it’s doubtful anyone ever called those function with in the keyword form. If so, sorry for any breakage but there’s no practical deprecation path to solve this ugly wart.

Accessing Attribute instances on class objects is now deprecated and will stop working in 2017. If you need introspection please use the __attrs_attrs__ attribute or the attr.fields function that carry them too. In the future, the attributes that are defined on the class body and are usually overwritten in your __init__ method are simply removed after @attr.s has been applied.

This will remove the confusing error message if you write your own __init__ and forget to initialize some attribute. Instead you will get a straightforward AttributeError. In other words: decorated classes will work more like plain Python classes which was always attrs‘s goal.
The serious business aliases attr.attributes and attr.attr have been deprecated in favor of attr.attrs and attr.attrib which are much more consistent and frankly obvious in hindsight. They will be purged from documentation immediately but there are no plans to actually remove them.

attr.asdict‘s dict_factory arguments is now propagated on recursion. #45
attr.asdict, attr.has and attr.fields are significantly faster. #48 #51
Add attr.attrs and attr.attrib as a more consistent aliases for attr.s and attr.ib.
Add frozen option to attr.s that will make instances best-effort immutable. #60
attr.asdict now takes retain_collection_types as an argument. If True, it does not convert attributes of type tuple or set to list. #69

Python 3.3 and 2.6 aren’t supported anymore. They may work by chance but any effort to keep them working has ceased.

The last Python 2.6 release was on October 29, 2013 and isn’t supported by the CPython core team anymore. Major Python packages like Django and Twisted dropped Python 2.6 a while ago already.

Python 3.3 never had a significant user base and wasn’t part of any distribution’s LTS release.

__slots__ have arrived! Classes now can automatically be slots-style (and save your precious memory) just by passing slots=True. #35
Allow the case of initializing attributes that are set to init=False. This allows for clean initializer parameter lists while being able to initialize attributes to default values. #32
attr.asdict can now produce arbitrary mappings instead of Python dicts when provided with a dict_factory argument. #40
Multiple performance improvements.

Add a convert argument to attr.ib, which allows specifying a function to run on arguments. This allows for simple type conversions, e.g. with attr.ib(convert=int). #26
Speed up object creation when attribute validators are used. #28

Add attr.validators.optional that wraps other validators allowing attributes to be None. #16
Fix multi-level inheritance. #24
Fix __repr__ to work for non-redecorated subclasses. #20

Initial release.